samedi 17 décembre 2016

After the smooth arrival of ESA’s latest Mars orbiter, mission controllers are now preparing it for the ultimate challenge: dipping into the Red Planet’s atmosphere to reach its final orbit.

The ExoMars Trace Gas Orbiter is on a multiyear mission to understand the tiny amounts of methane and other gases in Mars’ atmosphere that could be evidence for possible biological or geological activity.

Trace Gas Orbiter at Mars

Following its long journey from Earth, the orbiter fired its main engine on 19 October to brake sufficiently for capture by the planet’s gravity.

It entered a highly elliptical orbit where its altitude varies between about 250 km and 98 000 km, with each circuit taking about four Earth days.

Ultimately, however, the science goals and its role as a data relay for surface rovers mean the craft must lower itself into a near-circular orbit at just 400 km altitude, with each orbit taking about two hours.

Aerobraking: the ultimate challenge

Mission controllers will use ‘aerobraking’ to achieve this, commanding the craft to skim the wispy top of the atmosphere for the faint drag to steadily pull it down.

“The amount of drag is very tiny,” says spacecraft operations manager Peter Schmitz, “but after about 13 months this will be enough to reach the planned 400 km altitude while firing the engine only a few times, saving on fuel.”

ExoMars first year in orbit

During aerobraking, the team at ESA’s mission control in Darmstadt, Germany, must carefully monitor the craft during each orbit to ensure it is not exposed to too much friction heating or pressure.

The drag is expected to vary from orbit to orbit because of the changing atmospheric, dust storms and solar activity. This means ESA’s flight dynamics teams will have to measure the orbit repeatedly to ensure it does not drop too low, too quickly.

The aerobraking campaign is set to begin on 15 March, when Mars will be just over 300 million km from Earth, and will run until early 2018.

Stepping up to the start

Mission controllers are now working intensively to prepare the craft, the flight plan and ground systems for the campaign.

First, on 19 January, they will adjust the angle of the orbit with respect to the Mars equator to 74º so that science observations can cover most of the planet.

Next, to get into an orbit from where to start aerobraking, the high point will be reduced on 3 and 9 February, leaving the craft in a 200 x 33 475 km orbit that it completes every 24 hours.

Mission controllers

ESA mission controllers have some previous experience with aerobraking using Venus Express, although that was done at the end of the mission as a demonstration. NASA also used aerobraking to take the Mars Reconnaissance Orbiter and other spacecraft into low orbits at Mars.

“This will be our first time to use aerobraking to achieve an operational orbit, so we’re taking the extra time available now to ensure our plans are robust and cater for any contingencies,” says flight director Michel Denis.

Beginning to slow down

Aerobraking proper will begin on 15 March with a series of seven thruster firings, about one every three days, that will steadily lower the craft’s altitude at closest approach – from 200 km to about 114 km.

Flight dynamics team

“Then the atmosphere can start its work, pulling us down,” says Peter Schmitz. “If all goes as planned, very little fuel will then be needed until the end of aerobraking early in 2018, when final firings will circularise the 400 km orbit.”

No date has been set, but science observations can begin once the final orbit is achieved. In addition, the path will provide two to three overflights of each rover every day to relay signals.

Spacecraft A-OK

Overall, the spacecraft is in excellent health. On 30 November, it received an updated ‘operating system’. To date, only one ‘safe mode’ has been triggered, when a glitch caused the craft to reboot and wait for corrective commands. That happened during preliminary testing of the main engine, when a faulty configuration was quickly identified and fixed.

"We are delighted to be flying such an excellent spacecraft,” says Michel. “We have an exciting and challenging mission ahead of us.”

vendredi 16 décembre 2016

Animation above: Flying over the Atlantic Ocean offshore from Daytona Beach, Florida, a Pegasus XL rocket with eight Cyclone Global Navigation Satellite System, or CYGNSS, spacecraft is released from the Orbital ATK L-1011 Stargazer aircraft and the first stage ignites at 8:37 a.m. EST. The CYGNSS satellites will make frequent and accurate measurements of ocean surface winds throughout the life cycle of tropical storms and hurricanes. The data that CYGNSS provides will enable scientists to probe key air-sea interaction processes that take place near the core of storms, which are rapidly changing and play a crucial role in the beginning and intensification of hurricanes.Animation Credit: NASA TV.

NASA confirmed Friday morning that all eight spacecraft of its latest Earth science mission are in good shape. The Cyclone Global Navigation Satellite System (CYGNSS) will provide scientists with advanced technology to see inside tropical storms and hurricanes like never before.

CYGNSS launched into orbit at 8:37 a.m. EST Thursday aboard an Orbital ATK air-launched Pegasus XL launch vehicle. The rocket was dropped and launched from Orbital’s Stargazer L-1011 aircraft, which took off from Cape Canaveral Air Force Station in Florida, over the Atlantic Ocean, off the coast of central Florida.

“The launch of CYGNSS is a first for NASA and for the scientific community,” said Thomas Zurbuchen, associate administrator for the agency’s Science Mission Directorate in Washington. “As the first orbital mission in our Earth Venture program, CYGNSS will make unprecedented measurements in the most violent, dynamic, and important portions of tropical storms and hurricanes.”

The CYGNSS constellation will make frequent and accurate measurements of ocean surface winds in and near a hurricane’s inner core, including regions beneath the eyewall and intense inner rainbands that previously could not be measured from space. CYGNSS will do this by using both direct and reflected signals from existing GPS satellites to obtain estimates of surface wind speed over the ocean.

“CYGNSS will provide us with detailed measurements of hurricane wind speeds, an important indicator of a storm’s intensity,” said Christopher Ruf, CYGNSS principal investigator at the University of Michigan’s Department of Climate and Space Sciences and Engineering in Ann Arbor. “Ultimately, the measurements from this mission will help improve hurricane track and intensity forecasts.”

CYGNSS is the first orbital mission competitively selected by NASA’s Earth Venture program, managed by the Earth System Science Pathfinder (ESSP) Program Office at NASA’s Langley Research Center, Hampton, Virginia. This program focuses on low-cost, science-driven missions to enhance our understanding of the current state of Earth and its complex, dynamic system and enable continual improvement in the prediction of future changes.

“There is a feeling of pride and joy knowing that you have been a part of something that is much bigger than yourself and will potentially have a significant positive impact on the general public safety,” said Jim Wells, ESSP mission manager.

Southwest Research Institute in San Antonio led the development, integration and operation of the CYGNSS microsatellites. The Space Physics Research Laboratory at the University of Michigan College of Engineering leads the overall mission execution, and its Climate and Space Sciences and Engineering department leads the science investigation. The Earth Science Division of NASA’s Science Mission Directorate oversees the mission.

The NASA Launch Services Program, based at the agency’s Kennedy Space Center in Florida, was responsible for spacecraft/launch vehicle integration and launch management. Orbital ATK Corp. of Dulles, Virginia, provided the Pegasus XL launch service to NASA.

In 1900, astronomer Joseph Lunt made a discovery: Peering through a telescope at Cape Town Observatory, the British–South African scientist spotted this beautiful sight in the southern constellation of Grus (The Crane): a barred spiral galaxy now named IC 5201.

Over a century later, the galaxy is still of interest to astronomers. For this image, the NASA/ESA Hubble Space Telescope used its Advanced Camera for Surveys (ACS) to produce a beautiful and intricate image of the galaxy. Hubble’s ACS can resolve individual stars within other galaxies, making it an invaluable tool to explore how various populations of stars sprang to life, evolved, and died throughout the cosmos.

IC 5201 sits over 40 million light-years away from us. As with two thirds of all the spirals we see in the Universe — including the Milky Way — the galaxy has a bar of stars slicing through its center.

The hazards of lost sleep can range from on-the-job errors to chronic disease. People all around the world experience disruptions in circadian rhythm, or the body’s natural regulator for sleep and wake cycles based on a 24-hour schedule, every day. This instinctual process can be disrupted by abnormal work schedules, extensive traveling between time zones, and by daily life for International Space Station crew members, who could experience 16 sunrises a day.

Circadian misalignment and sleep deficiency occur during both short- and long-duration spaceflight, and can lead to significant, fatigue-induced errors and long-term sleep loss. In addition to spaceflight, employees working in Mission Control, where shift work and abnormal hours are common, often experience the effects of circadian misalignment. Chronic sleep deprivation and circadian desynchronization are associated with health complications such as metabolic disorders, cardiovascular diseases, gastrointestinal diseases and some types of cancers. NASA’s flight surgeons and scientists have devised tools for crew members and Mission Control employees to help promote a more natural circadian rhythm in space and during shift work back on Earth. Here are seven ways NASA addresses circadian rhythm disruption.

Image above: Solid-State Light Assemblies (SSLAs) are replacing old lighting technology aboard the International Space Station. These lights provide more efficient, longer-lasting lighting options, as well as provide crew members with the ability to adjust lighting intensity based on the time of day to promote a more conducive environment for both sleep and alertness. Image Credit: NASA.

1 - Schedule Sleep and Wake Times

Allowing the body time to prepare for situations where circadian misalignment may occur is the most effective countermeasure against sleep problems like insomnia and fatigue. Developing a schedule that takes into account human circadian rhythm and an individual’s typical sleeping habits is the first tool in ensuring optimal performance, alertness and sleep quality. In addition to noting sleep and wake times, schedules should include lighting instructions, diet, exercise and sleep aid information to ensure proper adaptation. Crew members follow a strict sleep and wake schedule for at least two days leading up to a launch or trainings that require international travel, and continue to follow a sleep schedule during spaceflight.

2 - Sleep Education and Training

Being aware of what factors impact sleep quality and quantity is important for promoting healthy sleep hygiene, or the behaviors, environmental conditions and other sleep-related factors that can affect sleep. Properly-timed exercise, minimizing light from digital devices in the evening, and thoughtful dietary choices can all lead to a better night’s sleep and help to prevent circadian misalignment.

3 - Sleep Environment

Every effort is made to provide space station crew members a sleeping environment that encourages healthy, undisrupted sleep times. Private sleeping quarters like those currently found aboard the station minimize the opportunity for disruption from other crew members and allow for varying sleep schedules. Other environmental factors that affect sleep for crew members aboard the station are temperature, lighting, airflow, noise, carbon dioxide and special restraints used to keep crew members from floating around while sleeping.

4 - Light

The space station orbits Earth every 90 minutes, which means the crew members see 16 sunrises each day. This frequent change from darkness to light severely impacts the body’s ability to adjust to a natural circadian rhythm. To combat this, lighting on the station is being transitioned from General Luminaire Assemblies (GLAs) to Solid-State Light Assemblies (SSLAs). SSLAs allow the crew members to adjust the color spectrum and intensity of the light to promote alertness and circadian resetting, or to promote sleep. Many laboratory investigations have shown that bright lights, when administered appropriately, provide a safe, reversible, non-pharmacological countermeasure to evoke alertness and enhance performance.

5 - Non-prescription Sleep and Alertness Substances

Melatonin and caffeinated products may be used to address circadian rhythm disruptions. Melatonin, a naturally produced hormone that functions to regulate day-night cycles, can help to facilitate circadian shifts during off-normal times.

6 - Sleep Cognitive Behavioral Therapy

Sleep Cognitive Behavioral Therapy (CBT) provides a solution to the random, unwanted thoughts that tend to cloud the mind just before bedtime and lead to the inability to naturally transition to sleep. Sleep CBT techniques help crew members to cope with the day’s events, pre-sleep preparation, adherence to sleep hygiene, engage in structured relaxation and psychological strategies such as cognitive restructuring. Sleep CBT helps crew members to leave undesirable sleep behaviors behind, and replace them with routines and techniques that promote good sleep.

7 - Pharmacologic Interventions

Once a crew member has exhausted the aforementioned options for successful circadian shifting techniques, options for pharmacological interventions are explored. Crew members may use three classes of medication to aid in sleep: chronobiologic, hypnotic and alertness. Prior to spaceflight, flight surgeons conduct ground testing on each crew member to test individual physiological response while using a variety of sleep-aid and alertness medication to ensure the safety and effectiveness of the crew.

Graphic above: Sleep schedules help not only crew members to prepare for a circadian shift, but also Mission Control Center employees, who often work shift work and other unusual schedules. Preparing the body for a circadian shift is the best way to avoid the potentially dangerous side effects that accompany a lack of sleep.Photo credit: Steven Lockley, Associate Professor of Medicine, Harvard University, Neuroscientist and member of NASA’s Fatigue Management Team and Dr. Smith Johnston, NASA Flight Surgeon, Medical Officer and Lead of NASA’s Fatigue Management Team. Graphic Credit: NASA.

Taking steps toward a better night’s sleep, whether on Earth or orbiting almost 250 miles above it, ensures faster response times, sharper cognitive skills, and an overall healthier mind and body. Learn more about the Lighting Effects investigation and keep up with the science happening aboard the station by following https://twitter.com/ISS_Research.

ESA’s Rosetta completed its incredible mission on 30 September, collecting unprecedented images and data right until the moment of contact with the comet's surface.

Rosetta’s final imaging sequence

Rosetta’s signal disappeared from screens at ESA’s mission control at 11:19:37 GMT, confirming that the spacecraft had arrived on the surface of Comet 67P/Churyumov–Gerasimenko and switched off some 40 minutes earlier and 720 million kilometres from Earth.

One of the final pieces of information received from Rosetta was sent by its navigation startrackers: a report of a ‘large object’ in the field of view – the comet horizon.

Rosetta's final descent

Reconstruction of the final descent showed that the spacecraft gently struck the surface only 33 m from the target point.

The accuracy once again highlighted the excellent work of the flight dynamics specialists who supported the entire mission.

The spot, just inside an ancient pit in the Ma’at region on the comet’s ‘head’, was named Sais, after a town where the Rosetta Stone was originally located.

Rosetta's last image

Numerous images were taken of the neighbouring pit, capturing incredible details of its layered walls that will be used to help decipher the comet’s geological history.

The final image was acquired about 20 m above the impact point. In addition, a number of Rosetta’s dust, gas and plasma analysis instruments collected data.

The pressure of the gas outflow from the comet was seen to rise as the surface neared. Scans revealed temperatures between about –190ºC and –110ºC down to a few centimetres below the surface. The variation was most likely due to shadows and local topography as Rosetta flew across the surface.

A last measurement of water vapour emission was made on 27 September, estimating the comet was emitting the equivalent of two tablespoons of water per second. During its most active period in August 2015, estimates were in the region of two bathtubs’ worth of water every second.

Comet landing sites in context

The first indications from spectral readings show there to be no significant differences in surface composition at the high resolutions obtained all the way down, and there was no obvious indication of small icy patches near the landing site.

The measurements also suggest an increase in very small dust grains – possibly around a millionth of a millimetre – close to the surface.

The last observation of the gas coma surrounding the comet was made the day before the final descent. Carbon dioxide was still being outgassed, at a greater distance from the Sun than when the comet was approaching it.

Stable solar wind conditions reigned during the final measurements of the solar wind and interplanetary magnetic field, providing ‘quiet’ background values that will be important for calibration.

Decreasing comet plasma densities were observed from about 2 km above the surface, with no obvious detection of local outgassing from the Ma’at pits.

Rosetta impact

Magnetic field measurements down to an estimated 11 m above the surface confirmed the previous observations of the comet as a non-magnetic body.

No large dust particles were collected during the descent, in itself an interesting result. First impressions are that the observed water vapour production was too low to lift dust grains above a detectable size from the surface.

Final spectra from Alice. Image courtesy A. Stern/J. Parker

“It’s great to have these first insights from Rosetta’s last set of data,” says Matt Taylor, ESA’s Rosetta Project Scientist. “Operations have been completed for over two months now, and the instrument teams are very much focused on analysing their huge datasets collected during Rosetta’s two-plus years at the comet.

“Data from this period will eventually be made available in our archives in the same way as all Rosetta data.”

jeudi 15 décembre 2016

A new statistical study of planets found by a technique called gravitational microlensing suggests that Neptune-mass worlds are likely the most common type of planet to form in the icy outer realms of planetary systems. The study provides the first indication of the types of planets waiting to be found far from a host star, where scientists suspect planets form most efficiently.

"We've found the apparent sweet spot in the sizes of cold planets. Contrary to some theoretical predictions, we infer from current detections that the most numerous have masses similar to Neptune, and there doesn't seem to be the expected increase in number at lower masses," said lead scientist Daisuke Suzuki, a post-doctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland Baltimore County. "We conclude that Neptune-mass planets in these outer orbits are about 10 times more common than Jupiter-mass planets in Jupiter-like orbits."

Gravitational microlensing takes advantage of the light-bending effects of massive objects predicted by Einstein's general theory of relativity. It occurs when a foreground star, the lens, randomly aligns with a distant background star, the source, as seen from Earth. As the lensing star drifts along in its orbit around the galaxy, the alignment shifts over days to weeks, changing the apparent brightness of the source. The precise pattern of these changes provides astronomers with clues about the nature of the lensing star, including any planets it may host.

"We mainly determine the mass ratio of the planet to the host star and their separation," said team member David Bennett, an astrophysicist at Goddard. "For about 40 percent of microlensing planets, we can determine the mass of the host star and therefore the mass of the planet."

Image above: This graph plots 4,769 exoplanets and planet candidates according to their masses and relative distances from the snow line, the point where water and other materials freeze solid (vertical cyan line). Gravitational microlensing is particularly sensitive to planets in this region. Planets are shaded according to the discovery technique listed at right. Masses for unconfirmed planetary candidates from NASA's Kepler mission are calculated based on their sizes. For comparison, the graph also includes the planets of our solar system. Image Credits: NASA's Goddard Space Flight Center.

More than 50 exoplanets have been discovered using microlensing compared to thousands detected by other techniques, such as detecting the motion or dimming of a host star caused by the presence of planets. Because the necessary alignments between stars are rare and occur randomly, astronomers must monitor millions of stars for the tell-tale brightness changes that signal a microlensing event.

However, microlensing holds great potential. It can detect planets hundreds of times more distant than most other methods, allowing astronomers to investigate a broad swath of our Milky Way galaxy. The technique can locate exoplanets at smaller masses and greater distances from their host stars, and it's sensitive enough to find planets floating through the galaxy on their own, unbound to stars.

NASA's Kepler and K2 missions have been extraordinarily successful in finding planets that dim their host stars, with more than 2,500 confirmed discoveries to date. This technique is sensitive to close-in planets but not more distant ones. Microlensing surveys are complementary, best probing the outer parts of planetary systems with less sensitivity to planets closer to their stars.

"Combining microlensing with other techniques provides us with a clearer overall picture of the planetary content of our galaxy," said team member Takahiro Sumi at Osaka University in Japan.

From 2007 to 2012, the Microlensing Observations in Astrophysics (MOA) group, a collaboration between researchers in Japan and New Zealand, issued 3,300 alerts informing the astronomical community about ongoing microlensing events. Suzuki's team identified 1,474 well-observed microlensing events, with 22 displaying clear planetary signals. This includes four planets that were never previously reported.

To study these events in greater detail, the team included data from the other major microlensing project operating over the same period, the Optical Gravitational Lensing Experiment (OGLE), as well as additional observations from other projects designed to follow up on MOA and OGLE alerts.

From this information, the researchers determined the frequency of planets compared to the mass ratio of the planet and star as well as the distances between them. For a typical planet-hosting star with about 60 percent the sun's mass, the typical microlensing planet is a world between 10 and 40 times Earth's mass. For comparison, Neptune in our own solar system has the equivalent mass of 17 Earths.

The results imply that cold Neptune-mass worlds are likely to be the most common types of planets beyond the so-called snow line, the point where water remained frozen during planetary formation. In the solar system, the snow line is thought to have been located at about 2.7 times Earth's mean distance from the sun, placing it in the middle of the main asteroid belt today.

Image above: Neptune-mass exoplanets like the one shown in this artist's rendering may be the most common in the icy regions of planetary systems. Beyond a certain distance from a young star, water and other substances remain frozen, leading to an abundant population of icy objects that can collide and form the cores of new planets. In the foreground, an icy body left over from this period drifts past the planet. Image Credits: NASA/Goddard/Francis Reddy.

"Beyond the snow line, materials that were gaseous closer to the star condense into solid bodies, increasing the amount of material available to start the planet-building process," said Suzuki. "This is where we think planetary formation was most efficient, and it's also the region where microlensing is most sensitive."

NASA's Wide Field Infrared Survey Telescope (WFIRST), slated to launch in the mid-2020s, will conduct an extensive microlensing survey. Astronomers expect it will deliver mass and distance determinations of thousands of planets, completing the work begun by Kepler and providing the first galactic census of planetary properties.

NASA's Ames Research Center manages the Kepler and K2 missions for NASA's Science Mission Directorate. The Jet Propulsion Laboratory (JPL) in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

WFIRST is managed at Goddard, with participation by JPL, the Space Telescope Science Institute in Baltimore, the Infrared Processing and Analysis Center, also in Pasadena, and a science team comprising members from U.S. research institutions across the country.

At first glance, Ceres, the largest body in the main asteroid belt, may not look icy. Images from NASA's Dawn spacecraft have revealed a dark, heavily cratered world whose brightest area is made of highly reflective salts -- not ice. But newly published studies from Dawn scientists show two distinct lines of evidence for ice at or near the surface of the dwarf planet. Researchers are presenting these findings at the 2016 American Geophysical Union meeting in San Francisco.

Animation above: This movie of images from NASA's Dawn spacecraft shows a crater on Ceres that is partly in shadow all the time. Such craters are called "cold traps." Dawn has shown that water ice could potentially be preserved in such place for very long amounts of time. Animation Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

"These studies support the idea that ice separated from rock early in Ceres’ history, forming an ice-rich crustal layer, and that ice has remained near the surface over the history of the solar system," said Carol Raymond, deputy principal investigator of the Dawn mission, based at NASA's Jet Propulsion Laboratory, Pasadena, California.

Water ice on other planetary bodies is important because it is an essential ingredient for life as we know it. "By finding bodies that were water-rich in the distant past, we can discover clues as to where life may have existed in the early solar system," Raymond said.

Ice is everywhere on Ceres

Ceres’ uppermost surface is rich in hydrogen, with higher concentrations at mid-to-high latitudes -- consistent with broad expanses of water ice, according to a new study in the journal Science.

"On Ceres, ice is not just localized to a few craters. It's everywhere, and nearer to the surface with higher latitudes," said Thomas Prettyman, principal investigator of Dawn's gamma ray and neutron detector (GRaND), based at the Planetary Science Institute, Tucson, Arizona.

Researchers used the GRaND instrument to determine the concentrations of hydrogen, iron and potassium in the uppermost yard (or meter) of Ceres. GRaND measures the number and energy of gamma rays and neutrons emanating from Ceres. Neutrons are produced as galactic cosmic rays interact with Ceres' surface. Some neutrons get absorbed into the surface, while others escape. Since hydrogen slows down neutrons, it is associated with fewer neutrons escaping. On Ceres, hydrogen is likely to be in the form of frozen water (which is made of two hydrogen atoms and one oxygen atom).

Image above: This graphic shows a theoretical path of a water molecule on Ceres. Some water molecules fall into cold, dark craters called "cold traps," where very little of the ice turns into vapor, even over the course of a billion years. Image Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Rather than a solid ice layer, there is likely to be a porous mixture of rocky materials in which ice fills the pores, researchers found. The GRaND data show that the mixture is about 10 percent ice by weight.

"These results confirm predictions made nearly three decades ago that ice can survive for billions of years just beneath the surface of Ceres," Prettyman said. "The evidence strengthens the case for the presence of near-surface water ice on other main belt asteroids."

Clues to Ceres' inner life

Concentrations of iron, hydrogen, potassium and carbon provide further evidence that the top layer of material covering Ceres was altered by liquid water in Ceres' interior. Scientists theorize that the decay of radioactive elements within Ceres produced heat that drove this alteration process, separating Ceres into a rocky interior and icy outer shell. Separation of ice and rock would lead to differences in the chemical composition of Ceres’ surface and interior.

Because meteorites called carbonaceous chondrites were also altered by water, scientists are interested in comparing them to Ceres. These meteorites probably come from bodies that were smaller than Ceres, but had limited fluid flow, so they may provide clues to Ceres' interior history. The Science study shows that Ceres has more hydrogen and less iron than these meteorites, perhaps because denser particles sunk while brine-rich materials rose to the surface. Alternatively, Ceres or its components may have formed in a different region of the solar system than the meteorites.

Ice in permanent shadow

A second study, led by Thomas Platz of the Max Planck Institute for Solar System Research, Gottingen, Germany, and published in the journal Nature Astronomy, focused on craters that are persistently in shadow in Ceres' northern hemisphere. Scientists closely examined hundreds of cold, dark craters called "cold traps" -- at less than minus 260 degrees Fahrenheit (110 Kelvin), they are so chilly that very little of the ice turns into vapor in the course of a billion years. Researchers found deposits of bright material in 10 of these craters. In one crater that is partially sunlit, Dawn's infrared mapping spectrometer confirmed the presence of ice.

This suggests that water ice can be stored in cold, dark craters on Ceres. Ice in cold traps has previously been spotted on Mercury and, in a few cases, on the moon. All of these bodies have small tilts with respect to their axes of rotation, so their poles are extremely cold and peppered with persistently shadowed craters. Scientists believe impacting bodies may have delivered ice to Mercury and the moon. The origins of Ceres' ice in cold traps are more mysterious, however.

"We are interested in how this ice got there and how it managed to last so long," said co-author Norbert Schorghofer of the University of Hawaii. "It could have come from Ceres' ice-rich crust, or it could have been delivered from space."

Regardless of its origin, water molecules on Ceres have the ability to hop around from warmer regions to the poles. A tenuous water atmosphere has been suggested by previous research, including the Herschel Space Observatory's observations of water vapor at Ceres in 2012-13. Water molecules that leave the surface would fall back onto Ceres, and could land in cold traps. With every hop there is a chance the molecule is lost to space, but a fraction of them ends up in the cold traps, where they accumulate.

Video above: This video shows a flyover of the intriguing crater named Occator on dwarf planet Ceres. Occator is home to Ceres' brightest area. Video Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

Ceres' brightest area, in the northern-hemisphere crater Occator, does not shine because of ice, but rather because of highly reflective salts. A new video produced by the German Aerospace Center (DLR) in Berlin simulates the experience of flying around this crater and exploring its topography. Occator's central bright region, which includes a dome with fractures, has recently been named Cerealia Facula. The crater's cluster of less reflective spots to the east of center is called Vinalia Faculae.

"The unique interior of Occator may have formed in a combination of processes that we are currently investigating," said Ralf Jaumann, planetary scientist and Dawn co-investigator at DLR. "The impact that created the crater could have triggered the upwelling of liquid from inside Ceres, which left behind the salts."

Dawn's next steps

Dawn began its extended mission phase in July, and is currently flying in an elliptical orbit more than 4,500 miles (7,200 kilometers) from Ceres. During the primary mission, Dawn orbited and accomplished all of its original objectives at Ceres and protoplanet Vesta, which the spacecraft visited from July 2011 to September 2012.

Dawn’s mission is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants, visit:

The adjournment was revoked by the Civil Court of the Waldensian Broye and North, said Thursday the Judicial Order of Vaud. The court ruled on Wednesday following the 6 December hearing. He revoked the adjournment and declared bankruptcy without prior prosecution of the company.

The court considered that "the conditions for prolonging the adjournment were no longer fulfilled". Swiss Space Systems Holding may lodge an appeal against the decision of the court within ten days.

Pascal Jaussi, CEO / Founder of Swiss Space Syrems (S3)

For weeks, the company of Pascal Jaussi is at the center of the attention because of its financial difficulties. S3 wants to launch mini-satellites from a shuttle from an airplane. The company also announced plans to organize weightless flights.

On the activity of his company, Pascal Jaussi said that "S3 does not make military equipment". He nevertheless points to the strategic importance of space and its control in the "world economic war". "We were threatened, tapped. Our servers have even been sabotaged. "

Dassault retires

Launched in 2013 and based in Payerne (VD), S3 has benefited from the support of Dassault Aviation, "a great industrialist who protects you from blows". When the French group withdrew in 2015, "we found ourselves vulnerable", which required the search for investors.

Pascal Jaussi says that the minor flights (Zero G) are scheduled for the end of January. "We will be on time for these flights. I do not doubt for a moment, because I have behind me a formidable team. Since the flights have been canceled.

Swiss Space Systems concept

At the end of August, Pascal Jaussi claimed to have been very violently assaulted in the woods of Aumont (FR). The investigation is still ongoing.

In spite of everything, this enterprise will be able to reborn from these ashes like the Phoenix! It still enjoys support in Switzerland. Courage Pascal!

The unique, air-launched vehicle was carried aloft by Orbital’s modified L-1011 aircraft, “Stargazer,” which took off from the Skid Strip runway at Cape Canaveral Air Force Station in Florida and deployed the three-stage Pegasus XL rocket at a predetermined drop point 39,000 feet above the Atlantic Ocean and about 110 nautical miles east-northeast of Daytona Beach.

“The deployments looked great — right on time,” said John Scherrer, CYGNSS Project Manager at the Southwest Research Institute and today’s CYGNSS mission manager.

“We think everything looks really, really good. About three hours after launch we’ll attempt first contact, and after that, we’ll go through a series of four contacts where we hit two [observatories] each time, checking the health and status of each spacecraft,” Scherrer added.

Prelaunch activities went smoothly throughout the morning, aided by good weather and healthy vehicles, according to NASA Launch Manager Tim Dunn of the agency’s Launch Services Program.

A NASA F-18 chase plane from Armstrong Flight Research Center in California provided visual contact and video of the conjoined Stargazer aircraft and Pegasus XL rocket.

The chase plane took to the skies minutes before the Stargazer went airborne at 7:38 a.m.

“It’s a beautiful day, with gorgeous weather,” Dunn said. “We had a nominal flyout, and all three stages performed beautifully. We had no issues at all with launch vehicle performance.”

Only 13 minutes after launch, the first pair of CYGNSS microsatellites deployed, with the rest releasing in pairs every 30 seconds.

“It’s a great event when you have a successful spacecraft separation – and with eight microsatellites, you get to multiply that times eight,” Dunn said.

CYGNSS Overview

“When the first two [observatories] came off, I started feeling good,” said CYGNSS Principal Investigator Chris Ruf of the University of Michigan. “When the last two came off, it felt fantastic. The orbit is right on the money of what we’ve been modeling.”

The team expects to begin getting science data next week, Ruf said. There will be a one- to two-month commissioning phase in which each microsatellite will be checked out and maneuvered into its final position.

The CYGNSS constellation is expected to be operational in time for the 2017 hurricane season. “Thanks, Pegasus and NASA, for a smooth ride,” Scherrer said.

Europe’s own Galileo satellite navigation system has begun operating, with the satellites in space delivering positioning, navigation and timing information to users around the globe.

Today, the European Commission, owner of the system, formally announced the start of Galileo Initial Services, the first step towards full operational capability.

Galileo coverage

Further launches will continue to build the satellite constellation, which will gradually improve the system performance and availability worldwide.

ESA has overseen the design and deployment of Galileo on behalf of the Commission, with system operations and service provision due to be entrusted to the European Global Navigation Satellite System Agency next year.

After five years of launches there are now 18 satellites in orbit. The most recent four, launched last month, are undergoing testing ahead of joining the constellation next spring.

Galileo satellites 15–18 prepared for liftoff

The full Galileo constellation will consist of 24 satellites plus orbital spares, intended to prevent any interruption in service.

ESA Director general Jan Woerner noted, “For ESA, this is a very important moment in the programme. We know that the performance of the system is excellent.

“The announcement of Initial Services is the recognition that the effort, time and money invested by ESA and the Commission has succeeded, that the work of our engineers and other staff has paid off, that European industry can be proud of having delivered this fantastic system.”

Galileo satellite

Paul Verhoef, ESA’s Director of the Galileo Programme and Navigation-related Activities, added, “Today’s announcement marks the transition from a test system to one that is operational. We are proud to be a partner in the Galileo programme.

“Still, much work remains to be done. The entire constellation needs to be deployed, the ground infrastructure needs to be completed and the overall system needs to be tested and verified.

“In addition, together with the Commission we have started work on the second generation, and this is likely to be a long but rewarding adventure.”

Initial Services

Galileo is now providing three service types, the availability of which will continue to be improved.

The Open Service is a free mass-market service for users with enabled chipsets in, for instance, smartphones and car navigation systems. Fully interoperable with GPS, combined coverage will deliver more accurate and reliable positioning for users.

Cospas–Sarsat system

Galileo’s Public Regulated Service is an encrypted, robust service for government-authorised users such as civil protection, fire brigades and the police.

The Search and Rescue Service is Europe’s contribution to the long-running Cospas–Sarsat international emergency beacon location. The time between someone locating a distress beacon when lost at sea or in the wilderness will be reduced from up to three hours to just 10 minutes, with its location determined to within 5 km, rather than the previous 10 km.

Finding your way

Like all satnav systems, Galileo operations rely on the extremely precise measurement of time – around 10 billionths of a second on average.

Because all electromagnetic waves, including radio, travel at a fixed speed – just under 30 cm each billionth of a second – the time it takes for Galileo signals to reach a user receiver yields distance measurements. All the receiver has to do is multiply the travel time by the speed of light.

Galileo constellation

A minimum of four satellites must be visible to pinpoint position: one each to fix latitude, longitude and altitude, with another to ensure synchronised timings. More satellites provide a greater level of service coverage and precision.

The public will begin benefiting as Galileo-capable devices enter the marketplace: 17 companies, representing more than 95% of global supply, now produce Galileo-ready chips.

Galileo System Time

‘Galileo System Time’ is set to become an important utility in its own right, essential for synchronising worldwide banking, power and data networks.

mercredi 14 décembre 2016

Scientists from NASA and three universities have presented new discoveries about the way heat and energy move and manifest in the ionosphere, a region of Earth’s atmosphere that reacts to changes from both space above and Earth below.

Far above Earth’s surface, within the tenuous upper atmosphere, is a sea of particles that have been split into positive and negative ions by the sun’s harsh ultraviolet radiation. Called the ionosphere, this is Earth's interface to space, the area where Earth's neutral atmosphere and terrestrial weather give way to the space environment that dominates most of the rest of the universe – an environment that hosts charged particles and a complex system of electric and magnetic fields. The ionosphere is both shaped by waves from the atmosphere below and uniquely responsive to the changing conditions in space, conveying such space weather into observable, Earth-effective phenomena – creating the aurora, disrupting communications signals, and sometimes causing satellite problems.

Image above: The ionosphere is a layer of charged particles in Earth’s atmosphere that extends from about 50 to 360 miles above the surface of Earth. Processes in the ionosphere also create bright swaths of color in the sky, known as airglow. Image Credit: NASA.

Many of these effects are not well-understood, leaving the ionosphere, for the most part, a region of mystery. Scientists from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, the Catholic University of America in Washington, D.C., the University of Colorado Boulder, and the University of California, Berkeley, presented new results on the ionosphere at the fall meeting of the American Geophysical Union on Dec. 14, 2016, in San Francisco.

One researcher explained how the interaction between the ionosphere and another layer in the atmosphere, the thermosphere, counteract heating in the thermosphere – heating that leads to expansion of the upper atmosphere, which can cause premature orbital decay. Another researcher described how energy outside the ionosphere accumulates until it discharges – not unlike lightning – offering an explanation for how energy from space weather crosses over into the ionosphere. A third scientist discussed two upcoming NASA missions that will provide key observations of this region, helping us better understand how the ionosphere reacts both to space weather and to terrestrial weather.

Changes in the ionosphere are primarily driven by the sun’s activity. Though it may appear unchanging to us on the ground, our sun is, in fact, a very dynamic, active star. Watching the sun in ultraviolet wavelengths of light from space – above our UV light-blocking atmosphere – reveals constant activity, including bursts of light, particles, and magnetic fields.

Occasionally, the sun releases huge clouds of particles and magnetic fields that explode out from the sun at more than a million miles per hour. These are called coronal mass ejections, or CMEs. When a CME reaches Earth, its embedded magnetic fields can interact with Earth’s natural magnetic field – called the magnetosphere – sometimes compressing it or even causing parts of it to realign.

It is this realignment that transfers energy into Earth’s atmospheric system, by setting off a chain reaction of shifting electric and magnetic fields that can send the particles already trapped near Earth skittering in all directions. These particles can then create one of the most recognizable and awe-inspiring space weather events – the aurora, otherwise known as the Northern Lights.

But the transfer of energy into the atmosphere isn’t always so innocuous. It can also heat the upper atmosphere – where low-Earth satellites orbit – causing it to expand like a hot-air balloon.

“This swelling means there’s more stuff at higher altitudes than we would otherwise expect,” said Delores Knipp, a space scientist at the University of Colorado Boulder. “That extra stuff can drag on satellites, disrupting their orbits and making them harder to track.”

Image above: The swelling of Earth’s upper atmosphere during geomagnetic storms can alter the orbits of satellites, bringing them lower and lower. Image Credit: NASA.

This phenomenon is called satellite drag. New research shows that this understanding of the upper atmosphere’s response to solar storms – and the resulting satellite drag – may not always hold true.

“Our basic understanding has been that geomagnetic storms put energy into the Earth system, which leads to swelling of the thermosphere, which can pull satellites down into lower orbits,” said Knipp, lead researcher on these new results. “But that isn’t always the case.”

Sometimes, the energy from solar storms can trigger a chemical reaction that produces a compound called nitric oxide in the upper atmosphere. Nitric oxide acts as a cooling agent at very high altitudes, promoting energy loss to space, so a significant increase in this compound can cause a phenomenon called overcooling.

“Overcooling causes the atmosphere to quickly shed energy from the geomagnetic storm much quicker than anticipated,” said Knipp. “It’s like the thermostat for the upper atmosphere got stuck on the ‘cool’ setting.”

That quick loss of energy counteracts the previous expansion, causing the upper atmosphere to collapse back down – sometimes to an even smaller state than it started in, leaving satellites traveling through lower-density regions than anticipated.

A new analysis by Knipp and her team classifies the types of storms that are likely to lead to this overcooling and rapid upper atmosphere collapse. By comparing over a decade of measurements from Department of Defense satellites and NASA’s Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics, or TIMED, mission, the researchers were able to spot patterns in energy moving throughout the upper atmosphere.

“Overcooling is most likely to happen when very fast and magnetically-organized ejecta from the sun rattle Earth’s magnetic field,” said Knipp. “Slow clouds or poorly-organized clouds just don’t have the same effect.”

This means that, counterintuitively, the most energetic solar storms are likely to provide a net cooling and shrinking effect on the upper atmosphere, rather than heating and expanding it as had been previously understood.

Competing with this cooling process is the heating caused by solar storm energy making its way into Earth’s atmosphere. Though scientists have known that solar wind energy eventually reaches the ionosphere, they have understood little about where, when and how this transfer takes place. New observations show that the process is localized and impulsive, and partly dependent on the state of the ionosphere itself.

Image above:: Earth's limb at night, seen from the International Space Station, with air glow visual composited into the image. Image Credit: NASA.

Traditionally, scientists have thought that the way energy moves throughout Earth’s magnetosphere and atmosphere is determined by the characteristics of the incoming particles and magnetic fields of the solar wind – for instance, a long, steady stream of solar particles would produce different effects than a faster, less consistent stream. However, new data shows that the way energy moves is much more closely tied to the mechanisms by which the magnetosphere and ionosphere are linked.

“The energy transfer process turns out to be very similar to the way lightning forms during a thunderstorm,” said Bob Robinson, a space scientist at NASA Goddard and the Catholic University of America.

During a thunderstorm, a buildup of electric potential difference – called voltage – between a cloud and the ground leads to a sudden, violent discharge of that electric energy in the form of lightning. This discharge can only happen if there’s an electrically conducting pathway between the cloud and the ground, called a leader.

Similarly, the solar wind striking the magnetosphere can build up a voltage difference between different regions of the ionosphere and the magnetosphere. Electric currents can form between these regions, creating the conducting pathway needed for that built-up electric energy to discharge into the ionosphere as a kind of lightning.

“Terrestrial lightning takes several milliseconds to occur, while this magnetosphere-ionosphere ‘lightning’ lasts for several hours – and the amount of energy transferred is hundreds to thousands of times greater,” said Robinson, lead researcher on these new results. These results are based on data from the global Iridium satellite communications constellation.

Because solar storms enhance the electric currents that let this magnetosphere-ionosphere lightning take place, this type of energy transfer is much more likely when Earth’s magnetic field is jostled by a solar event.

The huge energy transfer from this magnetosphere-ionosphere lightning is associated with heating of the ionosphere and upper atmosphere, as well as increased aurora.

Looking Forward

Though scientists are making progress in understanding the key processes that drive changes in the ionosphere and, in turn, on Earth, there is still much to be understood. In 2017, NASA is launching two missions to investigate this dynamic region: the Ionospheric Connection Explorer, or ICON, and Global Observations of the Limb and Disk, or GOLD.

“The ionosphere doesn’t only react to energy input by solar storms,” said Scott England, a space scientist at the University of California, Berkeley, who works on both the ICON and GOLD missions. “Terrestrial weather, like hurricanes and wind patterns, can shape the atmosphere and ionosphere, changing how they react to space weather.”

ICON will simultaneously measure the characteristics of charged particles in the ionosphere and neutral particles in the atmosphere – including those shaped by terrestrial weather – to understand how they interact. GOLD will take many of the same measurements, but from geostationary orbit, which gives a global view of how the ionosphere changes.

Animation above: NASA’s Ionospheric Connection Explorer, or ICON, and NASA’s Global-scale Observations of the Limb and Disk, or GOLD, mission will take complementary observations of Earth’s ionosphere and upper atmosphere. Animation Credit: NASA.

Observations of the Limb and Disk, or GOLD, mission will take complementary observations of Earth’s ionosphere and upper atmosphere. Credit: NASA

Both ICON and GOLD will take advantage of a phenomenon called airglow – the light emitted by gas that is excited or ionized by solar radiation – to study the ionosphere. By measuring the light from airglow, scientists can track the changing composition, density, and even temperature of particles in the ionosphere and neutral atmosphere.

ICON’s position 350 miles above Earth will enable it to study the atmosphere in profile, giving scientists an unprecedented look at the state of the ionosphere at a range of altitudes. Meanwhile, GOLD’s position 22,000 miles above Earth will give it the chance to track changes in the ionosphere as they move across the globe, similar to how a weather satellite tracks a storm.

“We will be using these two missions together to understand how dynamic weather systems are reflected in the upper atmosphere, and how these changes impact the ionosphere,” said England.

ICON and GOLD are Explorer-class missions. NASA Goddard manages the Explorer Program for NASA's Science Mission Directorate in Washington. UC Berkeley's Space Sciences Laboratory will develop the ICON mission and the two ultraviolet imaging spectrographs, the Naval Research Laboratory in Washington, D.C., will develop the MIGHTI instrument, the University of Texas in Dallas will develop the Ion Velocity Meter, and the ICON spacecraft is being built by Orbital ATK in Dulles, Virginia. GOLD is led by the University of Central Florida, and the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder is building the instrument.

NASA Goddard manages the TIMED mission for the Heliophysics Division within the Science Mission Directorate at NASA Headquarters in Washington. The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, built the spacecraft for NASA.

Image above: A member of the AWAKE collaboration, from the Max Planck Institute, performing tests in the experiment's underground tunnel (Image: Maximilien Brice/CERN).

The AWAKE collaboration has reached a major milestone; in the final week of CERN's accelerator operations for 2016, it has observed strong modulation of high-energy proton bunches in plasma, signaling the generation of very strong electromagnetic fields. This is a significant step towards the goal of using the proton-driven plasma wakefield technique to accelerate electrons.

The facility was successfully commissioned between June and November and the experiment took its first data in the final week of accelerator operations at CERN in 2016.

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) is the first facility investigating the use of plasma wakefields driven by proton beams to accelerate charged particles.

"The use of proton bunches to drive wakefields is of particular interest because of the large energy carried by the proton bunches from the CERN SPS and LHC accelerators," says the AWAKE spokesperson, Allen Caldwell, from the Max Planck Institute of Physics in Munich. "It allows for much longer acceleration stages than for other techniques," he points out.

The AWAKE experiment injects a "drive" bunch of protons from CERN’s SPS accelerator into a plasma column created by ionising a gas with a laser. When this bunch interacts with the plasma, it splits into a series of smaller bunches, in a process called self-modulation. As these shorter bunches move through the plasma, they generate a strong wakefield. It is the process of self-modulation that the AWAKE team has observed signals of, and from which it can infer the creation of the wakefield.

Graphic above: Image showing the simulation of the interaction between the bunches of protons (red dots) and the plasma wakefield (blue waves). (Image: Alexey Petrenko/CERN).

The next step, which AWAKE has yet to demonstrate, is to inject a second beam of electrons, the “witness” beam, in the right phase behind the proton beam. This witness beam "feels" the wakefield and is accelerated, just as a surfer accelerates by riding a wave.

The use of plasma to accelerate particles is a potential alternative to traditional accelerating methods that rely on radiofrequency electromagnetic cavities. It has long been known that plasmas are capable of supporting very strong electric fields. The challenge for researchers is to understand the best way to take advantage of this capability in order to create future compact and powerful particle accelerators at reasonable costs. The fields generated by plasma wakefields driven by proton beams could be up to two orders of magnitude higher than fields achievable using conventional radio-frequency cavities.

“To have observed indications for the first time of proton bunch self-modulation, after just a few days of tests is an excellent achievement. It's down to a very motivated and dedicated team," grins Edda Gschwendtner, AWAKE technical coordinator and CERN AWAKE project leader.

"We now plan to study this process in detail in 2017. We hope then to demonstrate the acceleration of electrons in the wake of the proton bunch,” adds Patric Muggli, AWAKE physics coordinator from CERN and the Max Planck Institute for Physics in Munich.

This exciting development, the culmination of three years of intense preparation, opens a new era of particle accelerator development at CERN and worldwide.

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.